Debug.Assert lets you check various things during the debugging process or when you are a debug build.

One of the problems with Debug.Assert is that it pops up a MessageBox dialog. UI dialogs are a big no-no in server applications since there are scenarios in which this UI dialog will never be show and your server application will simply get stuck waiting for someone to push the buttons of the dialog.

One of the most common cases in which you will not see the dialog is when your server application runs under different credentials than your currently logged on user. In that case the UI dialog will hide somewhere in a different sessions without any chance of being seen by any other user.

.NET employs various huristics to figure out when to display the assert dialog. In most cases, in a server application it will not show the assert dialog at all (even in debug builds). As far as I could tell (and its currently just an calculated guess), if you have a debugger installed and registered as a debugger, .NET WILL display the dialog and that may pose a problem if your server application runs under different credentials than the currently logged on user.

It seems there is a way to overcome this by using a configuration flag.

Add the following section to your web.config (or app.config for applications other than ASP.NET) and it will disable poping up a UI window in your application which make cause it to deadlock: